In an Intelligent Transportation System (ITS), various types of information related to transportation are obtained in a timely manner through vehicle to vehicle (V2V) communication, vehicle to infrastructure (V2I) communication, vehicle-to-pedestrian (V2P) communication, or vehicle-to-network (V2N) communication. These communication manners may be collectively referred to as vehicle to X (V2X) communication. X is a collective term for vehicles, road infrastructure, pedestrians, and networks.
When a V2X message is transmitted using a Long Term Evolution (LTE) technology, two user equipments (UE) may be directly connected to each other for communication. When the two UEs are directly connected to each other for communication, an eNB first configures a transmission resource pool for the UE. The UE selects a transmission resource in an idle state from the transmission resource pool in a manner in which a transmission resource is selected after channel sensing is performed. Then, the UE sends the V2X message by using the transmission resource in the idle state. The manner in which a transmission resource is selected after channel sensing is performed is as follows. The UE senses each transmission resource in the transmission resource pool, where a typical value of sensing duration is 1000 ms; and then determines the transmission resource in the idle state based on a sensing result.
In the foregoing manner, the transmission resource in the idle state can be selected only after at least 1000-ms sensing duration. Therefore, the manner is not applicable to all V2X message sending scenarios. In some specific sending scenarios, for example, after the UE initially obtains configuration information of the transmission resource pool, even though there is a to-be-transmitted V2X message, the UE needs to wait for the 1000-ms sensing duration, and then select the transmission resource in the idle state to send the V2X message. Because a transmission delay of the V2X message is 100 ms or 20 ms, the UE may fail to send the V2X message after waiting for the 1000-ms sensing duration.